Milo g



(No Model.)

M. KELLOGG. MULTIPLE SWITGHBOARD.

Patented Oct. 26,1897.

Line/1 I IIVVENTOR 7% @almimm MNINL 1' XIV} G V 5 M H w 4 ATTORNEYS.

NITF TA'IES MILO G. KELLOGG, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE KELLOGG SWI'lCIIBOARD AND SUPPLY COMPANY, OF SAME PLACE.

MULTIPLE SWITCH BOARD.

SPECIFICATION forming part of Letters Patent No. 592,381, dated October 26, 1897.

Application filed August 5, 1890. Serial No. 361,107. (No model.)

To all whom it may concern.-

Be it known that I, MILO G. KELLOGG, of Chicago, in the county of Cook and State of Illinois, temporarily residing at Stuttgart, in the Empire of Germany, have invented certain new and useful Improvements in Multiple Switchboards for Telephone-Exchanges, of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawings, forming a part of this specification.

My invention relates to a telephone-exchange system in which the lines are singlecircuit lines grounded at their outer ends and normally grounded at the central office; and it consists in a system of testing the lines to determine whether they are in use.

In the drawings illustrating my invention, Figures 1 and 1 represent sections of two multiple switchboards of the exchange to which the same lines are connected. Fig. 2 shows a diagram of the boards with the mainline apparatus and connections necessary to illustrate my invention. Fig. 3 shows a diagram of an operators cord system to be used in connection with the boards. Fig. 4 shows an operators test system to be used at the board. Fig. 5 shows a subscribeWs-station apparatus. I

In Fig. 2, A is a sectional view of the switchboard shown in Fig. 1, and A is a sectional view of the switchboard shown in Fig. 1 each as indicated by the line (1 e.

I place as many boards in the central office as are found necessary or desirable in order to properly operate the exchange. On each board is a springjack or other suitable switch for each line. Each switch has a contactspring which normally connects with an insulated contact-piece and is adapted to receive a loop-plugand,when a plug is inserted, to disconnect the spring from the contactpiece and connect the two contact-pieces of the plug with the spring and said insulated contact-piece, respectively. The switch is also adapted to receive a single contact switch-plug and, when a plug is inserted, to disconnect the spring from the contact-piece and connect the spring with the contactpiece of the plug.

In the construction of the switches as shown and as will hereinafter be described I prefer to have a contact-point electrically connected with the contact-piece and on which the spring normally bears, as there is less chance of poor connection when the spring bears on a point than when it bears 011 a surface adapted to be brought into connection with the plugcontacts.

In Fig. 2, g 9 represent thesprings of the different switches,,h h the contact-points on which the springs normally bear, and j 7' the contact-pieces of the switches connected with the points h h. Z Z are the switch-holes. a I) are the rubber strips 011 which the metal parts of the switches are mounted, as shown, and through the fronts of which are the switchholesZ l. The contact-piecesjj are so placed along one of the surfaces of the plug-holes as readily to form connection with one of the contact-pieces of the loop-plugs. The holes Z Z are adapted to receive the switch-plugs shown in Fig. 3 and marked D D, and when a plug is inserted into a switch it raises the spring 9 from the contact-point h and the spring g and the contact-piece of the plug are in contact. Theseholes are also adapted to receive the loop plug shownin Fig. 4, and when a plug is inserted into a hole it raises the spring of the switch from the contactpoint It and the spring g and the contactpiece j of the switch are in contact with the two contact-pieces of the plug, respectively.

w and as are calling-annunciators, one for each of the lines shown. Each annunciator has a pair of contact-points normally (or when the annunciator does not indicate'a call) in contact with each other, but which are separated by the annunciator while it indicates a call. The two contact-points of a pair are marked 1) and q, respectively. One of'them, q, is a spring-contact, whichis pressed by the annunciator-drop when the drop falls away from its corresponding contact-point p. The contact-point p is represented as an anglepiece which passes over the spring q and is in contact with the spring when the spring is not actuated by the annunciator-drop.

B is a test-battery placed in the common ground wire or connection of the lines.

Two lines are shown in the drawings, one marked line No. 1 and the other line No. 2.

These lines are ordinary single-circuit lines grounded at their outer ends and having at the subscribers stations any usual and apboards, passing in each case to the spring first.

It then passes through its line-annunciator and the pair of contact-points of the annunciator to the common ground wire or connection in which is the test-battery B. The circuit of each line shown may thus be traced in Fig. 2.

In the operators cord system shown in Fig. 3,1) D are the switch-plugs of a'pair-ot' cords. n n are the rubber insulations of the plugs, and m m are their contact-pieces. These contact-pieces pass each to the bottom of its plug and are adapted to rest normally, or when the plug is not in use, on the metal piece 0, which then connects it with the ground. Weights, as is usual, or similar devices may be used to bring the contact-pieces of the plugs into contact with the piece 0 and secure a good connection. These plugs are adapted to be inserted into any of the switches at their board, and when a plug is inserted it operates the switch, as above described. The plugs should be inserted so that the contact-piece m is in contact with the spring g. The connections of the lines might have been reversed, so that the lines pass first to the contact-pieces j of each of their switches, and in that case the plugs should be inserted in such a position that their contact-pieces form connection with the piecesj of the switches. Y is the looping-in switch for the pair of cords shown. K is the calling-key, and 'v is a clearing-out annu'nciator. tis the operators telephone, and B is her calling generator or battery. The circuits are substantially as shown.

The operation of the system in connection with the switchboards will be apparent to those skilled in the art. It will readily be apparent that when a line is switched by the insertion of a plug into its switch the line is disconnected from its normal ground-wire at the central office in which is the test-battery B and is connected into a circuit with the pair of cords. Only one pair of cords is shown, but the connection of such other pairs, with their accompanying apparatus, as the operator may need will be apparent to those skilled in the art. To each pair of cords, with its plugs, belong a looping-in switch, a clearing-out annunciator, and a calling-key. One telephone and one calling generator will answer for her system of cords.

In the operators test system shown in Fig. 4, T is a loop test-plug adapted to be inserted into any of the switches and when inserted to operate them, as heretofore described, and S is a test receiving instrument. The instrument is connected in a loop which terminates in the two contact-pieces of the plug and is operated under the conditions hereinafter stated when included in circuit with the test-battery B. Each operator has one cord system and one test system, and they are conveniently mounted and arranged for her work.

In the subscribers-station apparatus shown in Fig. 5, 1 is the telephone-switch. 2 is the calling-generator. 3 is the signal-receiving bell. 4 is the subscribers telephone. 5 is the secondary, and 6 is the primary, of the induction-coil. 7 is the transmitter. 8 is the transmitter-battery. 9 is a condenser. 10 is a resistance-coil of suitable resistance. These parts may be of usual forms of apparatus, and are connected as shown or in other ways, so as to perform practically the operations required and the operations hereinafter described.

The condenser and resistance-coil at the subscribers station are connected in the apparatus in multiple or parallel circuit to each other.

When the subscribers telephone is on its switch, the signal-receiving bell is in the circuit of the line, and the telephone, the secondary of the induction-coil, and the condenser and resistance coil are shunted by a wire of small resistance, so as to be practically out of the circuit. Vhen the telephone is off the switch, the telephone, the secondary of the induction-coil, and the condenser and resistance-coil in parallel circuit are in the circuit and the signal-bell is practically out of the circuit.

The test receiving instruments and testbatteries should be so constructed and adjusted to each other and the circuits that the instrument will sound or respond when it and the battery are looped into the closed circuit of any single line and the subscribers telephone is not oir" its switch for use, but will not respond if the circuitis open at any point or if the subscribers telephone is off its switch and the condenser and resistance-coil at the subscribers station are included in the circuit in parallel circuit or the line is switched with another line and thereby has its testcircuit open, as willhereinafterbeindicated.

The operation of the test system is as follows: hen an operator desires to test a line, she places her test-plug into the switch of the line and by so doing disconnects the points 9 and h of the switch and connects them with the contact-pieces of the plug. If, then, the line is not switched at any board and the annunciator does not indicate a call and the subscribers telephone is on its switch, the test receiving instrument will sound or respend, indicating that the line is free to be switched to. If, however, the line not being switched, the subscriber has sent in a call and the annunciator indicates the call or has taken his telephone from the switch for use, the instrument will not sound, as the line being open at the annunciator-points or the and the test is made in the cut-oft portion of the linethat is, that portion which is between the switch used for switching and the oiiice ground-the instrument will not sound, because the test'circuit is open at the pair of contact-points of the switch used for switching. If, again, the line is switched at any board with another line, and the test is made in some switch between the one used for switching and the subscribers station, the instrument will not sound on account of the battery being cut off from the circuit in which the test receiving instrument is included. \Vhen a test of a line is made and the test receiving instrument sounds, the operator knows that neither the line nor the operators telephone is switched for use nor the line-annunciator indicates a call, and when the instrument does not sound she knows that either the annunciator indicates acall or the subscribers telephone is switched for use or the line is switched for use, and she will not connect the line with any other line. By this system a subscribers line is reserved to himself from the time he sends in his call or takes the telephone down for use.

In multiple-switchboard systems an opera tor to whom certain lines are assigned to answer frequently receives several calls at practically the same moment, and it may require some time before she can switch to a certain line and answer its call. In systems in which the test depends only on the line being switched at some board another operator may in the meantime test the line, and, finding it to test free, may switch it with another line and cause annoyance and confusion to the subscriber. This cannot occur in this system of testing, because as soon as the subscriber takes his telephone from its switch the line will test busy whether or not it is switched at the central otlice. Again, in systems of testing which depend only on the subscribers telephone being on or oiil' its switch confusion frequently arises "from the fact that a subscriber places his telephone on its switch when he is through conversation without sending in a clearing-out signal, and his line tests free and is connected to when it is already switched with another line. Lines in this condition are technically called tied up. This again cannot occur in this system, because the line will test busy until it is disconnected at the central office whether or not the subscribers telephone is on its switch. The system therefore combines the advantages and obviates the disadvantages of the two general systems of testing outlined above. Moreover, in this system the line tests busy as soon as the calling-generator operates, and the annunciatorindicates a call, whether the subscriber may have taken down his telephone for use or have replaced it on its switch.

I claim as myinvention and desire to secure by Letters Patent- 1. In a telephone-exchange system, a telephone-line normally on closed circuit and containing a test-battery in the circuit, in combination with an annunciator normally in the circuit of the line, having contact-points by which the circuit is open while the annunciator indicates a call, a subscribers-station apparatus containing a telephone, atelephoneswitch, a condenser and resistance-coil in derived circuit, contacts and connections by which said condenser and resistance-coil in derived circuit are included in the circuit of the line while the telephone is switched for use and only then, a test receiving instrument and switching apparatus for looping the same into'such normally closed circuit, said instrument being constructed and adjusted to sound or respond when looped into such circuit and neither the telephone is switched for use nor the annunciator indicates a call and not to sound or respond when either the telephone is switched or the annunciator indicates a call, substantially as set forth.

2. In a telephone-exchange system, telephone-lines normally on closed circuit and each having a test-battery in circuit, in combination with an annunciator normally in the circuit of each line, with contact-points by which the line-circuit is open when the an nunciator indicates a call, a subscribefls-sta tion apparatus for each line, containing a telephone, a telephone-switch, a condenser and resistancecoil in parallel circuit, contacts and connections by which said condenser and resistancecoil in parallel circuit are included in the circuit of the line while the telephone is switched for use and only then, a test receiving instrument and switch apparatus for looping the same into the normal circuit of either line, said instrument being constructed and adjusted to sound or respond when looped into the line-circuit and neither the telephone is switched nor the annunciator indicates a call and not to sound or respond when either the telephone is thus switched or the annunciator thus indicates, substantially as set forth.

3. In a telephone-exchange system, ground circuit lines normally on closed circuit and containing a testbattery in their common ground-wire, in combination with an annunciator normally in the circuit of each line, each annunciator having a pair of contactpoints by which its line-circuit is open while the annunciator indicates a call, a subscribers-station apparatus for each line, containing a telephone, a telephone-switch, a condenser and resistance-coil in parallel circuit, contacts and connections by which said condenser and resistance-coil in parallel circuit are includedin the circuit of the line while the telephone is switched for use and only then, a test receiving instrument and switch apparatus for looping the same into the normal circuit'of any line, said instrument being so constructed and so adjusted as to sound when looped into the circuit and neither the subscribers telephone is switched for use nor the annunciator indicates a call and not to sound or respond when either the telephone is thus switched or the annunciator thus indicates, substantially as set forth.-

4. In a telephone-exchange system, a telephone-line normally on closed circuit, in combination with an annunciator normally in the circuit of the line, having contact-points by which the circuit is open while the annunciator indicates a call, a subscribers-station apparatus containing a telephone, a telephoneswitch, a condenser and resistance-coil in derived circuit, contacts and connections by which said condenser and resistance-coil in derived circuit are included in the circuit of the line while the telephone is switched for use and only then, a test receiving instrument, switching apparatus for looping the same into the normal circuit of the line and a battery in the circuit thereby established, said instrument being so constructed and adjusted as to sound or respond when included in such circuit and neither the telephone is switched for use nor the annunciator indicates a call and not to sound or respond when either the telephone is thus switched or the annunciator thus indicates, substantially as set forth,

5. In a telephone-exchange system, telephone-lines grounded at their outer ends and multiple switchboards for the same, each board containing a switch for each line, each switch having a pair of contact-points normally in contact, adapted to receive a switchplug and when the plug is inserted 'into the switch to have the pair of contact-points of the switch separated and the contact-piece of the plug in contact with the line contact-point of the switch, and adapted to receive a loop test-plug and when the plug is inserted into the switch to have the pair of contact-points of the switch separated and connection made between them and the contact-pieces of the plug, respectively, each line passing successively through the pairs of contact-points of its switches, passing in each case to the line contact-point first and from the last switch to the ground, in combination with an annunciator normally in the circuit of each line, each annunciator having a pair of contactpoints by which its circuit is open while it indicates a call, a test-battery normally in circuit with'each' line, a subscribers-station apparatus for each line, containing a telephone, a telephone-switch, a condenser and resistance-coil in derived circuit, contacts and connections by which the condenser and resistance-coil in derived circuit are included in the circuit of the line while the telephone is' switched for use and only then, and a test receiving instrument at each board, included in a loop the two ends of which terminate in the two contact-pieces of a loop test-plug, each instrument being constructed and ad justed to sound or respond when it is included in the normal circuit of either line and neither the line nor the telephone is switched for use nor the annunciator indicates a call and not to sound or respond when either the line or the telephone is switched or the annunciator indicates a call, substantially as set forth.

In witness whereof I hereunto subscribe my name this 23d day of June, 1890.

MILO G. KELLOGG. WVitnesses:

EMIL ABENHEIM, ABBOTT L. MILLS. 

